A More Informative Map: Inverting Thermal Orbital Phase and Eclipse Lightcurves of Exoplanets
E. Rauscher, V. Suri, and N. B. Cowan

TL;DR
This paper introduces a novel orthogonal eigencurve method using principal component analysis for exoplanet thermal mapping, enabling more efficient, model-independent, and sensitive eclipse and phase curve analysis, demonstrated on HD 189733b.
Contribution
It develops a new PCA-based eigencurve approach for exoplanet mapping that improves computational efficiency and reduces parameter correlations, applicable to combined phase and eclipse data.
Findings
Eigensurves are orthogonal and ranked by sensitivity.
Eclipse mapping is more sensitive to flux concentration than hotspot offset.
First brightness temperature map of HD 189733b's dayside.
Abstract
Only one exoplanet has so far been mapped in both longitude and latitude, but the James Webb Space Telescope should provide mapping-quality data for dozens of exoplanets. The thermal phase mapping problem has previously been solved analytically, with orthogonal maps---spherical harmonics---yielding orthogonal lightcurves---sinusoids. The eclipse mapping problem, let alone combined phase+eclipse mapping, does not lend itself to such a neat solution. Previous efforts have either adopted spherical harmonics, or various ad hoc map parameterizations, none of which produce orthogonal lightcurves. We use principal component analysis to construct orthogonal "eigencurves," which we then use to fit published 8 micron observations of the hot Jupiter HD 189733b. This approach has a few advantages over previously used techniques: 1) the lightcurves can be pre-computed, accelerating the fitting…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astro and Planetary Science · Geophysics and Gravity Measurements
